Six classes of diffraction-based optoelectronic instruments have been invented as means for wavelength-based processing of light. One family of anticipated applications lies in scientific instrumentation for studying chemical and physical reactions that affect and/or are affected differently by light of different wavelengths or different combinations of wavelengths. Another family of anticipated applications lies in optoelectronic communication systems.
An instrument of the first class is basically a spectrometer that can serve as a building block for the instruments of the other classes. In this instrument, a beam of light emitted from the site of a chemical or physical reaction strikes a diffraction grating, which causes each of its wavelength components to propagate in a direction that depends on its wavelength. Photodetectors are positioned to receive light diffracted to different angular intervals that, by virtue of the aforementioned diffraction, correspond to different wavelength bands. Hence, the photodetector outputs are indicative of the time-dependent intensities of light emitted by the chemical or physical reaction in the selected wavelength bands.
In an instrument of the second class, the input light comprises two beams. In one of two possible modes of operation, the purpose served by the instrument is to help determine whether the beams are correlated sufficiently to be considered as having originated from the same source. In the other mode of operation, one of the beams is a reference beam and the instrument is used to compare the other beam with the reference beam. The two incoming beams impinge from different directions on a diffraction grating. As in the first instrument, the diffracted light from each beam impinges on photodetectors corresponding to various wavelength bands. In this case, there are two sets of photodetectors - one for each incoming beam. The outputs of the photodetectors as functions of time are sampled and the samples used to compute correlations between the time-dependent spectra of the two beams. The correlation values are taken to be indications of the relatedness or unrelatedness of the incoming beams.
In an instrument of the third class, a beam of light is split into two beams, which are then diffracted into wavelength components. One set of wavelength-component beams passes through a chamber containing a medium (hereafter denoted the altered medium) that could be undergoing a reaction that one seeks to study. The other set of wavelength-component beams passes through an otherwise identical chamber that contains a reference medium. After passage through the chambers, the two sets of wavelength-component beams impinge on photodetectors that are arranged in one or two sets, depending on the number and arrangement of diffraction gratings. The outputs of the photodetectors are sampled and processed to analyze differences between the effects of the altered and reference media on the light propagating through them.
The instruments of the fourth class can exist in diverse forms. Common to all forms is the use of diffraction gratings to split beams of light from multiple sources into wavelength components, which are then made to impinge on reaction sites to determine whether light at those wavelengths does or does not promote the reactions in question. In some cases reactions may be promoted by light of different wavelengths impinging in specified sequences within short intervals of time; the instruments of this class can be designed to generate the required sequences and measure their effects.
An instrument of the fifth class includes two coaxial cylinders. The outer surface of the inner cylinder is covered with a diffraction grating. The outer cylinder holds an array of photodetectors that intercept light diffracted by the grating. The cylinders can be translated axially and/or rotated, relative to each other, to change the wavelength range of the monitored light.
An instrument of the sixth class is a beam-steering device for data communication. A light beam modulated to convey symbols impinges successively on two diffraction gratings. The direction(s) of diffraction depend(s) on the wavelength(s) present in the beam. Hence, diffraction can be used to steer the beam, according to its wavelength, to one or more desired photodetector(s) in an array.
This work was done by Stevan Spremo ofAmes Research Center, Peter Fuhr of San Jose State University Foundation, and John Schipper, Law Offices of John Schipper. For further information, access the Technical Support Package (TSP)free on-line at www.techbriefs.com/tsp under the Physical Sciences category.
Inquiries concerning rights for the commercial use of this invention should be addressed to
the Patent Counsel
Ames Research Center
Refer to ARC-14650.